Chapter 24: Energy and Energy Resources
Chapter 24: Energy and Energy Resources
Chapter 24: Energy and Energy Resources
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sections<br />
1 What is energy?<br />
2 <strong>Energy</strong> Transformations<br />
Lab Hearing with Your Jaw<br />
3 Sources of <strong>Energy</strong><br />
Lab <strong>Energy</strong> to Power Your Life<br />
Virtual Lab What are the<br />
relationships between kinetic<br />
energy <strong>and</strong> potential energy?<br />
(bkgd.)Chris Knapton/Science Photo Library/Photo Researchers<br />
<strong>Energy</strong> <strong>and</strong> <strong>Energy</strong><br />
<strong>Resources</strong><br />
Blowing Off Steam<br />
The electrical energy you used today might<br />
have been produced by a coal-burning<br />
power plant like this one. <strong>Energy</strong> contained<br />
in coal is transformed into heat, <strong>and</strong> then<br />
into electrical energy. As boiling water<br />
heated by the burning coal is cooled, steam<br />
rises from these cone-shaped cooling towers.<br />
Science Journal Choose three devices that use<br />
electricity, <strong>and</strong> identify the function of each device.
Marbles <strong>and</strong> <strong>Energy</strong><br />
What’s the difference between a moving<br />
marble <strong>and</strong> one at rest? A moving marble<br />
can hit something <strong>and</strong> cause a change to<br />
occur. How can a marble acquire energy—<br />
the ability to cause change?<br />
1. Make a track on a<br />
table by slightly separating<br />
two metersticks<br />
placed side by side.<br />
2. Using a book, raise<br />
one end of the track<br />
slightly <strong>and</strong> measure<br />
the height.<br />
3. Roll a marble down the track. Measure the<br />
distance from its starting point to where it<br />
hits the floor. Repeat. Calculate the average<br />
of the two measurements.<br />
4. Repeat steps 2 <strong>and</strong> 3 for three different<br />
heights. Predict what will happen if you<br />
use a heavier marble. Test your prediction<br />
<strong>and</strong> record your observations.<br />
5. Think Critically In your Science Journal,<br />
describe how the distance traveled by the<br />
marble is related to the height of the<br />
ramp. How is the motion of the marble<br />
related to the ramp height?<br />
Start-Up Activities<br />
<strong>Energy</strong> Make the following<br />
Foldable to help identify what<br />
you already know, what you<br />
want to know, <strong>and</strong> what you learned about<br />
energy.<br />
STEP 1<br />
STEP 2<br />
STEP 3<br />
Fold a vertical sheet<br />
of paper from side to<br />
side. Make the front<br />
edge about 1 cm<br />
shorter than the back<br />
edge.<br />
Turn lengthwise<br />
<strong>and</strong> fold into thirds<br />
Unfold, cut, <strong>and</strong> label each tab for<br />
only the top layer along both folds to<br />
make three tabs.<br />
Know? Like to<br />
Learned?<br />
know?<br />
Identify Questions Before you read the chapter,<br />
write what you know <strong>and</strong> what you want to know<br />
about the types, sources, <strong>and</strong> transformation of<br />
energy under the appropriate tabs. As you read<br />
the chapter, correct what you have written <strong>and</strong><br />
add more questions under the Learned tab.<br />
Preview this chapter’s content<br />
<strong>and</strong> activities at<br />
green.msscience.com<br />
715<br />
(bkgd.)Chris Knapton/Science Photo Library/Photo Researchers, (inset)Matt Meadows
■ Explain what energy is.<br />
■ Distinguish between kinetic<br />
energy <strong>and</strong> potential energy.<br />
■ Identify the various forms of<br />
energy.<br />
<strong>Energy</strong> is involved whenever a<br />
change occurs.<br />
Review Vocabulary<br />
mass: a measure of the amount<br />
of matter in an object<br />
New Vocabulary<br />
• energy<br />
•<br />
kinetic energy<br />
•<br />
potential energy<br />
•<br />
thermal energy<br />
•<br />
chemical energy<br />
•<br />
radiant energy<br />
•<br />
electrical energy<br />
nuclear energy<br />
What is energy?<br />
716 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
(l c)file photo, (r)Mark Burnett<br />
The Nature of <strong>Energy</strong><br />
What comes to mind when you hear the word energy? Do you<br />
picture running, leaping, <strong>and</strong> spinning like a dancer or a gymnast?<br />
How would you define energy? When an object has energy, it can<br />
make things happen. In other words, energy is the ability to cause<br />
change. What do the items shown in Figure 1 have in common?<br />
Look around <strong>and</strong> notice the changes that are occurring—<br />
someone walking by or a ray of sunshine that is streaming through<br />
the window <strong>and</strong> warming your desk. Maybe you can see the wind<br />
moving the leaves on a tree. What changes are occurring?<br />
Transferring <strong>Energy</strong> You might not realize it, but you have a<br />
large amount of energy. In fact, everything around you has<br />
energy, but you notice it only when a change takes place.<br />
Anytime a change occurs, energy is transferred from one object<br />
to another. You hear a footstep because energy is transferred<br />
from a foot hitting the ground to your ears. Leaves are put into<br />
motion when energy in the moving wind is transferred to them.<br />
The spot on the desktop becomes warmer when energy is transferred<br />
to it from the sunlight. In fact, all objects, including leaves<br />
<strong>and</strong> desktops, have energy.<br />
Figure 1 <strong>Energy</strong> is the ability to cause change.<br />
Explain how these objects cause change.
<strong>Energy</strong> of Motion<br />
Things that move can cause change. A bowling ball rolls<br />
down the alley <strong>and</strong> knocks down some pins, as in Figure 2A. Is<br />
energy involved? A change occurs when the pins fall over. The<br />
bowling ball causes this change, so the bowling ball has energy.<br />
The energy in the motion of the bowling ball causes the pins to<br />
fall. As the ball moves, it has a form of energy called kinetic<br />
energy. Kinetic energy is the energy an object has due to its<br />
motion. If an object isn’t moving, it doesn’t have kinetic energy.<br />
Kinetic <strong>Energy</strong> <strong>and</strong> Speed If you roll the<br />
bowling ball so it moves faster, what happens<br />
when it hits the pins? It might knock down<br />
more pins, or it might cause the pins to go flying<br />
farther. A faster ball causes more change to<br />
occur than a ball that is moving slowly. Look at<br />
Figure 2B. The professional bowler rolls a fastmoving<br />
bowling ball. When her ball hits the<br />
pins, pins go flying faster <strong>and</strong> farther than for a<br />
slower-moving ball. All that action signals that<br />
her ball has more energy. The faster the ball<br />
goes, the more kinetic energy it has. This is true<br />
for all moving objects. Kinetic energy increases<br />
as an object moves faster.<br />
How does kinetic energy<br />
depend on speed?<br />
Kinetic <strong>Energy</strong> <strong>and</strong> Mass Suppose, as<br />
shown in Figure 2C, you roll a volleyball down<br />
the alley instead of a bowling ball. If the volleyball<br />
travels at the same speed as a bowling ball,<br />
do you think it will send pins flying as far? The<br />
answer is no. The volleyball might not knock<br />
down any pins. Does the volleyball have less<br />
energy than the bowling ball even though they<br />
are traveling at the same speed?<br />
An important difference between the volleyball<br />
<strong>and</strong> the bowling ball is that the volleyball has<br />
less mass. Even though the volleyball is moving<br />
at the same speed as the bowling ball, the volleyball<br />
has less kinetic energy because it has less<br />
mass. Kinetic energy also depends on the mass of<br />
a moving object. Kinetic energy increases as the<br />
mass of the object increases.<br />
This ball<br />
has kinetic<br />
energy because<br />
it is rolling<br />
down the alley.<br />
This ball<br />
has more kinetic<br />
energy because it<br />
has more speed.<br />
This ball<br />
has less kinetic<br />
energy because<br />
it has less mass.<br />
Figure 2 The kinetic energy<br />
of an object depends on the mass<br />
<strong>and</strong> speed of the object.<br />
SECTION 1 What is energy? 717<br />
(t b)Bob Daemmrich, (c)Al Tielemans/Duomo
Figure 3 The potential<br />
energy of an object depends on<br />
its mass <strong>and</strong> height above the<br />
ground.<br />
Determine which vase has<br />
more potential energy, the red<br />
one or the blue one.<br />
Figure 4 The hotter an object is,<br />
the more thermal energy it has. A<br />
cup of hot chocolate has more thermal<br />
energy than a cup of cold water,<br />
which has more thermal energy than<br />
a block of ice with the same mass.<br />
718 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
KS Studios<br />
<strong>Energy</strong> of Position<br />
An object can have energy even though<br />
it is not moving. For example, a glass of<br />
water sitting on the kitchen table doesn’t<br />
have any kinetic energy because it isn’t moving.<br />
If you accidentally nudge the glass <strong>and</strong><br />
it falls on the floor, changes occur. Gravity<br />
pulls the glass downward, <strong>and</strong> the glass has<br />
energy of motion as it falls. Where did this<br />
energy come from?<br />
When the glass was sitting on the table,<br />
it had potential (puh TEN chul) energy.<br />
Potential energy is the energy stored in an<br />
object because of its position. In this case,<br />
the position is the height of the glass above<br />
the floor. The potential energy of the glass<br />
changes to kinetic energy as the glass falls.<br />
The potential energy of the glass is greater if<br />
it is higher above the floor. Potential energy<br />
also depends on mass. The more mass an object has, the more<br />
potential energy it has. Which object in Figure 3 has the most<br />
potential energy?<br />
Forms of <strong>Energy</strong><br />
Food, sunlight, <strong>and</strong> wind have energy, yet they seem different<br />
because they contain different forms of energy. Food <strong>and</strong><br />
sunlight contain forms of energy different from the kinetic<br />
energy in the motion of the wind. The warmth you feel from<br />
sunlight is another type of energy that is different from the<br />
energy of motion or position.<br />
Thermal <strong>Energy</strong> The feeling of warmth from sunlight signals<br />
that your body is acquiring more thermal energy. All<br />
objects have thermal energy that increases as its temperature<br />
increases. A cup of hot chocolate has more thermal energy than<br />
a cup of cold water, as shown in Figure 4.<br />
Similarly, the cup of water has more thermal<br />
energy than a block of ice of the same mass.<br />
Your body continually produces thermal<br />
energy. Many chemical reactions that take<br />
place inside your cells produce thermal<br />
energy. Where does this energy come from?<br />
Thermal energy released by chemical reactions<br />
comes from another form of energy<br />
called chemical energy.
Chemical <strong>Energy</strong> When you eat a meal, you are putting a<br />
source of energy inside your body. Food contains chemical<br />
energy that your body uses to provide energy for your brain, to<br />
power your movements, <strong>and</strong> to fuel your growth. As in Figure 5,<br />
food contains chemicals, such as sugar, which can be broken<br />
down in your body. These chemicals are made of atoms that are<br />
bonded together, <strong>and</strong> energy is stored in the bonds between<br />
atoms. Chemical energy is the energy stored in chemical bonds.<br />
When chemicals are broken apart <strong>and</strong> new chemicals are<br />
formed, some of this energy is released. The flame of a c<strong>and</strong>le is<br />
the result of chemical energy stored in the wax. When the wax<br />
burns, chemical energy is transformed into thermal energy <strong>and</strong><br />
light energy.<br />
When is chemical energy released?<br />
Light <strong>Energy</strong> Light from the c<strong>and</strong>le flame travels through the<br />
air at an incredibly fast speed of 300,000 km/s. This is fast<br />
enough to circle Earth almost eight times in 1 s. When light<br />
strikes something, it can be absorbed, transmitted, or reflected.<br />
When the light is absorbed by an object, the object can become<br />
warmer. The object absorbs energy from the light <strong>and</strong> this<br />
energy is transformed into thermal energy. Then energy carried<br />
by light is called radiant energy. Figure 6 shows a coil of wire<br />
that produces radiant energy when it is heated. To heat the<br />
metal, another type of energy can be used—electrical energy.<br />
Figure 5 Complex chemicals in food store<br />
chemical energy. During activity, the chemical<br />
energy transforms into kinetic energy.<br />
Sugar<br />
Figure 6 Electrical energy is<br />
transformed into thermal energy in<br />
the metal heating coil. As the<br />
metal becomes hotter, it emits<br />
more radiant energy.<br />
SECTION 1 What is energy? 719<br />
(l r)Bob Daemmrich, (b)Andrew McClenaghan/Science Photo Library/Photo Researchers
Figure 7 Complex power plants<br />
are required to obtain useful energy<br />
from the nucleus of an atom.<br />
Summary<br />
The<br />
•<br />
Nature of <strong>Energy</strong><br />
•<br />
<strong>Energy</strong> is the ability to cause change.<br />
Kinetic energy is the energy an object has<br />
due to its motion. Kinetic energy depends on<br />
•<br />
an object’s speed <strong>and</strong> mass.<br />
Potential energy is the energy an object has<br />
due to its position. Potential energy depends<br />
on an object’s height <strong>and</strong> mass.<br />
•Forces of <strong>Energy</strong><br />
Thermal energy increases as temperature<br />
•<br />
increases.<br />
Chemical energy is the energy stored in chem-<br />
•<br />
ical bonds in molecules.<br />
Light energy, also called radiant energy, is the<br />
•<br />
energy contained in light.<br />
Electrical energy is the energy carried by elec-<br />
•<br />
tric current.<br />
Nuclear energy is the energy contained in the<br />
nucleus of an atom.<br />
720 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
Mark Burnett/Photo Researchers<br />
Electrical <strong>Energy</strong> Electrical lighting is<br />
one of the many ways electrical energy is<br />
used. Look around at all the devices that use<br />
electricity. Electric current flows in these<br />
devices when they are connected to batteries or<br />
plugged into an electric outlet. Electrical<br />
energy is the energy that is carried by an electric<br />
current. An electric device uses the electrical<br />
energy provided by the current flowing in<br />
the device. Large electric power plants generate<br />
the enormous amounts of electrical energy<br />
used each day. About 20 percent of the electrical<br />
energy used in the United States is generated<br />
by nuclear power plants.<br />
Nuclear <strong>Energy</strong> Nuclear power plants use the energy stored in<br />
the nucleus of an atom to generate electricity. Every atomic<br />
nucleus contains energy—nuclear energy—that can be transformed<br />
into other forms of energy. However, releasing the nuclear<br />
energy is a difficult process. It involves the construction of complex<br />
power plants, shown in Figure 7. In contrast, all that is<br />
needed to release chemical energy from wood is a lighted match.<br />
Self Check<br />
1. Explain why a high-speed collision between two cars<br />
would cause more damage than a low-speed collision<br />
between the same two cars.<br />
2. Describe the energy transformations that occur when a<br />
piece of wood is burned.<br />
3. Identify the form of energy that is converted into thermal<br />
energy by your body.<br />
4. Explain how, if two vases are side by side on a shelf,<br />
one could have more potential energy.<br />
5. Think Critically A golf ball <strong>and</strong> a bowling ball are moving<br />
<strong>and</strong> both have the same kinetic energy. Which one is<br />
moving faster? If they move at the same speed, which<br />
one has more kinetic energy?<br />
6. Communicate In your Science Journal, record different<br />
ways the word energy is used. Which ways of<br />
using the word energy are closest to the definition of<br />
energy given in this section?<br />
green.msscience.com/self_check_quiz
<strong>Energy</strong> Transformations<br />
Changing Forms of <strong>Energy</strong><br />
Chemical, thermal, radiant, <strong>and</strong> electrical are some of the<br />
forms that energy can have. In the world around you, energy is<br />
transforming continually between one form <strong>and</strong> another. You<br />
observe some of these transformations by noticing a change in<br />
your environment. Forest fires are a dramatic example of an<br />
environmental change that can occur naturally as a result of<br />
lightning strikes. A number of changes occur that involve energy<br />
as the mountain biker in Figure 8 pedals up a hill. What energy<br />
transformations cause these changes to occur?<br />
Tracking <strong>Energy</strong> Transformations As the mountain biker<br />
pedals, his leg muscles transform chemical energy into kinetic<br />
energy. The kinetic energy of his leg muscles transforms into<br />
kinetic energy of the bicycle as he pedals. Some of this energy<br />
transforms into potential energy as he moves up the hill. Also,<br />
some energy is transformed into thermal energy. His body is<br />
warmer because chemical energy is being released. Because of<br />
friction, the mechanical parts of the bicycle are warmer, too.<br />
<strong>Energy</strong> in the form of heat is almost always one of the products<br />
of an energy transformation. The energy transformations that<br />
occur when people exercise, when cars run, when living things<br />
grow <strong>and</strong> even when stars explode, all produce heat.<br />
■ Apply the law of conservation of<br />
energy to energy transformations.<br />
■ Identify how energy changes<br />
form.<br />
■ Describe how electric power<br />
plants produce energy.<br />
Changing energy from one form to<br />
another is what makes cars run, furnaces<br />
heat, telephones work, <strong>and</strong><br />
plants grow.<br />
Review Vocabulary<br />
transformation: a change in<br />
composition or structure<br />
New Vocabulary<br />
• law of conservation of energy<br />
• generator<br />
• turbine<br />
Figure 8 The ability to transform energy<br />
allows the biker to climb the hill.<br />
Identify all the forms of energy that are<br />
represented in the photograph.<br />
SECTION 2 <strong>Energy</strong> Transformations 721<br />
Lori Adamski Peek/Stone/Getty Images
Topic: <strong>Energy</strong><br />
Transformations<br />
Visit green.msscience.com for Web<br />
links to information about energy<br />
transformations that occur during<br />
different activities <strong>and</strong> processes.<br />
Activity Choose an activity or<br />
process <strong>and</strong> make a graph showing<br />
how the kinetic <strong>and</strong> potential<br />
energy change during it.<br />
Figure 9 During the flight of the<br />
baseball, energy is transforming<br />
between kinetic <strong>and</strong> potential<br />
energy.<br />
Determine where the ball has the<br />
most kinetic energy. Where does the<br />
ball have the most total energy?<br />
722 CHAPTER <strong>24</strong><br />
Richard Hutchings<br />
The Law of Conservation of <strong>Energy</strong><br />
It can be a challenge to track energy as it moves from object<br />
to object. However, one extremely important principle can serve<br />
as a guide as you trace the flow of energy. According to the<br />
law of conservation of energy, energy is never created or<br />
destroyed. The only thing that changes is the form in which<br />
energy appears. When the biker is resting at the summit, all his<br />
original energy is still around. Some of the energy is in the form<br />
of potential energy, which he will use as he coasts down the hill.<br />
Some of this energy was changed to thermal energy by friction<br />
in the bike. Chemical energy was also changed to thermal energy<br />
in the biker’s muscles, making him feel hot. As he rests, this thermal<br />
energy moves from his body to the air around him. No<br />
energy is missing—it can all be accounted for.<br />
Can energy ever be lost? Why or why not?<br />
Changing Kinetic <strong>and</strong> Potential <strong>Energy</strong><br />
The law of conservation of energy can be used to identify the<br />
energy changes in a system. For example, tossing a ball into the<br />
air <strong>and</strong> catching it is a simple system. As shown in Figure 9, as<br />
the ball leaves your h<strong>and</strong>, most of its energy is kinetic. As the ball<br />
rises, it slows <strong>and</strong> its kinetic energy decreases. But, the total<br />
energy of the ball hasn’t changed. The decrease in kinetic energy<br />
equals the increase in potential energy as the ball flies higher in<br />
the air. The total amount of energy remains constant. <strong>Energy</strong><br />
moves from place to place <strong>and</strong> changes form, but it never is created<br />
or destroyed.<br />
Kinetic<br />
energy<br />
Potential<br />
energy<br />
Kinetic<br />
energy
Figure 10 Hybrid cars that use an electric motor <strong>and</strong><br />
a gasoline engine for power are now available. Hybrid<br />
cars make energy transformations more efficient.<br />
Gasoline<br />
engine<br />
<strong>Energy</strong> Changes Form<br />
<strong>Energy</strong> transformations occur constantly all around you.<br />
Many machines are devices that transform energy from one<br />
form to another. For example, an automobile engine transforms<br />
the chemical energy in gasoline into energy of motion.<br />
However, not all of the chemical energy is converted into<br />
kinetic energy. Instead, some of the chemical energy is converted<br />
into thermal energy, <strong>and</strong> the engine becomes hot. An<br />
engine that converts chemical energy into more kinetic energy<br />
is a more efficient engine. New types of cars, like the one shown<br />
in Figure 10, use an electric motor along with a gasoline<br />
engine. These engines are more efficient so the car can travel<br />
farther on a gallon of gas.<br />
Transforming Chemical <strong>Energy</strong><br />
Inside your body, chemical energy also is<br />
transformed into kinetic energy. Look at Figure 11. The transformation<br />
of chemical to kinetic energy occurs in muscle cells.<br />
There, chemical reactions take place that cause certain molecules<br />
to change shape. Your muscle contracts when many of<br />
these changes occur, <strong>and</strong> a part of your body moves.<br />
The matter contained in living organisms, also called biomass,<br />
contains chemical energy. When organisms die, chemical<br />
compounds in their biomass break down. Bacteria, fungi, <strong>and</strong><br />
other organisms help convert these chemical compounds to<br />
simpler chemicals that can be used by other living things.<br />
Thermal energy also is released as these changes occur. For<br />
example, a compost pile can contain plant matter, such as grass<br />
clippings <strong>and</strong> leaves. As the compost pile decomposes, chemical<br />
energy is converted into thermal energy. This can cause the temperature<br />
of a compost pile to reach 60°C.<br />
Generator<br />
Battery<br />
Electric<br />
motor<br />
Analyzing <strong>Energy</strong><br />
Transformations<br />
Procedure<br />
1. Place soft clay on the floor<br />
<strong>and</strong> smooth out its surface.<br />
2. Hold a marble 1.5 m<br />
above the clay <strong>and</strong> drop it.<br />
Measure the depth of the<br />
crater made by the marble.<br />
3. Repeat this procedure<br />
using a golf ball <strong>and</strong> a<br />
plastic golf ball.<br />
Analysis<br />
1. Compare the depths of the<br />
craters to determine which<br />
ball had the most kinetic<br />
energy as it hit the clay.<br />
2. Explain how potential<br />
energy was transformed<br />
into kinetic energy during<br />
your activity.<br />
SECTION 2 <strong>Energy</strong> Transformations 723<br />
Ron Kimball/Ron Kimball Photography
Figure 11<br />
Paddling a raft, throwing<br />
a baseball, playing the<br />
violin — your skeletal<br />
muscles make these <strong>and</strong><br />
countless other body movements<br />
possible. Muscles work<br />
by pulling, or contracting. At<br />
the cellular level, muscle contractions<br />
are powered by reactions<br />
that transform chemical<br />
energy into kinetic energy.<br />
<strong>Energy</strong> transformations<br />
taking place in<br />
your muscles provide<br />
the power to move.<br />
▼<br />
Skeletal muscles are made<br />
up of bundles of muscle cells, or<br />
fibers. Each fiber is composed of<br />
many bundles of muscle filaments.<br />
▼<br />
7<strong>24</strong> CHAPTER <strong>24</strong><br />
(t)Judy Lutz, (b)Lennart Nilsson<br />
Skeletal muscle<br />
VISUALIZING ENERGY TRANSFORMATIONS<br />
Bundle<br />
of muscle<br />
fibers<br />
Filament<br />
bundle<br />
Muscle fiber<br />
Muscle<br />
filaments<br />
Muscle<br />
fibers<br />
Biceps<br />
Triceps<br />
Many skeletal muscles are arranged<br />
in pairs that work in opposition to each<br />
other. When you bend your arm, the<br />
biceps muscle contracts, while the triceps<br />
relaxes. When you extend your arm the<br />
triceps contracts, <strong>and</strong> the biceps relaxes.<br />
▼<br />
A signal from a nerve fiber starts a<br />
chemical reaction in the muscle filament.<br />
This causes molecules in the muscle filament<br />
to gain energy <strong>and</strong> move. Many<br />
filaments moving together cause the<br />
muscle to contract.<br />
▼<br />
Nerve fiber
Figure 12 The simple act of listening to a radio involves<br />
many energy transformations. A few are diagrammed here.<br />
Electrical<br />
energy of<br />
radio signal<br />
Kinetic<br />
energy<br />
of speaker<br />
Sound<br />
energy<br />
of air<br />
Kinetic energy<br />
of eardrum<br />
<strong>and</strong> fluid<br />
Transforming Electrical <strong>Energy</strong> Every day you use electrical<br />
energy. When you flip a light switch, or turn on a radio or television,<br />
or use a hair drier, you are transforming electrical<br />
energy to other forms of energy. Every time you plug something<br />
into a wall outlet, or use a battery, you are using electrical<br />
energy. Figure 12 shows how electrical energy is transformed<br />
into other forms of energy when you listen to a radio. A loudspeaker<br />
in the radio converts electrical energy into sound waves<br />
that travel to your ear—energy in motion. The energy that is<br />
carried by the sound waves causes parts of the ear to move also.<br />
This energy of motion is transformed again into chemical <strong>and</strong><br />
electrical energy in nerve cells, which send the energy to your<br />
brain. After your brain interprets this energy as a voice or music,<br />
where does the energy go? The energy finally is transformed into<br />
thermal energy.<br />
Transforming Thermal <strong>Energy</strong> Different forms of energy<br />
can be transformed into thermal energy. For example, chemical<br />
energy changes into thermal energy when something burns.<br />
Electrical energy changes into thermal energy when a wire that<br />
is carrying an electric current gets hot. Thermal energy can be<br />
used to heat buildings <strong>and</strong> keep you warm. Thermal energy also<br />
can be used to heat water. If water is heated to its boiling point,<br />
it changes to steam. This steam can be used to produce kinetic<br />
energy by steam engines, like the steam locomotives that used to<br />
pull trains. Thermal energy also can be transformed into radiant<br />
energy. For example, when a bar of metal is heated to a high<br />
temperature, it glows <strong>and</strong> gives off light.<br />
Electrical energy<br />
of brain <strong>and</strong><br />
nerve cells<br />
Controlling Body<br />
Temperature Most<br />
organisms have some<br />
adaptation for controlling<br />
the amount of thermal<br />
energy in their bodies.<br />
Some living in cooler climates<br />
have thick fur<br />
coats that help prevent<br />
thermal energy from<br />
escaping, <strong>and</strong> some living<br />
in desert regions<br />
have skin that helps keep<br />
thermal energy out.<br />
Research some of the<br />
adaptations different<br />
organisms have for controlling<br />
the thermal<br />
energy in their bodies.<br />
SECTION 2 <strong>Energy</strong> Transformations 725
Figure 13 Thermal energy<br />
moves from the hot chocolate<br />
to the cooler surroundings.<br />
Explain what happens to the hot<br />
chocolate as it loses thermal energy.<br />
Figure 14 A coal-burning power<br />
plant transforms the chemical<br />
energy in coal into electrical energy.<br />
List some of the other energy<br />
sources that power plants use.<br />
726 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
KS Studios<br />
Coal supply<br />
River or reservoir<br />
Chemical energy<br />
in coal<br />
Conveyor<br />
belt<br />
How Thermal <strong>Energy</strong> Moves Thermal energy<br />
can move from one place to another. Look at<br />
Figure 13. The hot chocolate has thermal energy<br />
that moves from the cup to the cooler air around<br />
it, <strong>and</strong> to the cooler spoon. Thermal energy only<br />
moves from something at a higher temperature to<br />
something at a lower temperature.<br />
Generating Electrical <strong>Energy</strong><br />
The enormous amount of electrical energy<br />
that is used every day is too large to be stored in<br />
batteries. The electrical energy that is available for<br />
use at any wall socket must be generated continually<br />
by power plants. Every power plant works on<br />
the same principle—energy is used to turn a large<br />
generator. A generator is a device that transforms kinetic energy<br />
into electrical energy. In fossil fuel power plants, coal, oil, or natural<br />
gas is burned to boil water. As the hot water boils, the steam<br />
rushes through a turbine, which contains a set of narrowly<br />
spaced fan blades. The steam pushes on the blades <strong>and</strong> turns the<br />
turbine, which in turn rotates a shaft in the generator to produce<br />
the electrical energy, as shown in Figure 14.<br />
Thermal energy<br />
in water<br />
Kinetic energy<br />
of steam<br />
What does a generator do?<br />
Kinetic energy<br />
of turbine<br />
Stack Steam line Turbine Generator<br />
Boiler<br />
Cooling water<br />
Electrical energy<br />
out of generator<br />
Transformer<br />
that increases<br />
voltage
Power Plants Almost 90 percent of the electrical<br />
energy generated in the United States is produced by<br />
nuclear <strong>and</strong> fossil fuel power plants, as shown in<br />
Figure 15. Other types of power plants include hydroelectric<br />
(hi droh ih LEK trihk) <strong>and</strong> wind. Hydroelectric<br />
power plants transform the kinetic energy of<br />
moving water into electrical energy. Wind power<br />
plants transform the kinetic energy of moving air into<br />
electrical energy. In these power plants, a generator<br />
converts the kinetic energy of moving water or wind<br />
to electrical energy.<br />
To analyze the energy transformations in a power<br />
plant, you can diagram the energy changes using arrows. A coalburning<br />
power plant generates electrical energy through the following<br />
series of energy transformations.<br />
chemical thermal kinetic kinetic electrical<br />
energy → energy → energy → energy → energy<br />
of coal of water of steam of turbine out of<br />
generator<br />
Nuclear power plants use a similar series of transformations.<br />
Hydroelectric plants, however, skip the steps that change water<br />
into steam because the water strikes the turbine directly.<br />
Summary<br />
Changing<br />
•<br />
Forms of <strong>Energy</strong><br />
Heat usually is one of the forms of energy pro-<br />
•<br />
duced in energy transformations.<br />
The law of conservation of energy states that<br />
energy cannot be created or destroyed; it can<br />
•<br />
only change form.<br />
The total energy doesn’t change when an<br />
•<br />
energy transformation occurs.<br />
As an object rises <strong>and</strong> falls, kinetic <strong>and</strong> potential<br />
energy are transformed into each other,<br />
but the total energy doesn’t change.<br />
•Generating Electrical <strong>Energy</strong><br />
A generator converts kinetic energy into elec-<br />
•<br />
trical energy.<br />
Burning fossil fuels produces thermal energy<br />
•<br />
that is used to boil water <strong>and</strong> produce steam.<br />
In a power plant, steam is used to spin a turbine<br />
which then spins an electric generator.<br />
green.msscience.com/self_check_quiz<br />
Coal<br />
51%<br />
Nuclear<br />
20%<br />
Gas<br />
14%<br />
Hydro<br />
9%<br />
Oil<br />
3%<br />
Other<br />
renewable<br />
3%<br />
Figure 15 The graph shows<br />
sources of electrical energy in the<br />
United States.<br />
Name the energy source that you<br />
think is being used to provide the<br />
electricity for the lights overhead.<br />
Self Check<br />
1. Describe the conversions between potential <strong>and</strong><br />
kinetic energy that occur when you shoot a basketball<br />
at a basket.<br />
2. Explain whether your body gains or loses thermal<br />
energy if your body temperature is 37°C <strong>and</strong> the<br />
temperature around you is 25°C.<br />
3. Describe a process that converts chemical energy to<br />
thermal energy.<br />
4. Think Critically A lightbulb converts 10 percent of<br />
the electrical energy it uses into radiant energy.<br />
Make a hypothesis about the other form of energy<br />
produced.<br />
5. Use a Ratio How many times greater is the amount of<br />
electrical energy produced in the United States by<br />
coal-burning power plants than the amount produced<br />
by nuclear power plants?<br />
SECTION 2 <strong>Energy</strong> Transformations 727
You probably have listened to music using<br />
speakers or headphones. Have you ever considered<br />
how energy is transferred to get the<br />
energy from the radio or CD player to your<br />
brain? What type of energy is needed to power<br />
the radio or CD player? Where does this energy<br />
come from? How does that energy become<br />
sound? How does the sound get to you? In this<br />
activity, the sound from a radio or CD player is<br />
going to travel through a motor before entering<br />
your body through your jaw instead of your<br />
ears.<br />
Real-World Question<br />
How can energy be transferred from a radio or<br />
CD player to your brain?<br />
Goals<br />
■ Identify energy transfers <strong>and</strong><br />
transformations.<br />
■ Explain your observations using the law of<br />
conservation of energy.<br />
Materials<br />
radio or CD player<br />
small electrical motor<br />
headphone jack<br />
Procedure<br />
1. Go to one of the places in the room with a<br />
motor/radio assembly.<br />
2. Turn on the radio or CD player so that you<br />
hear the music.<br />
3. Push the headphone jack into the headphone<br />
plug on the radio or CD player.<br />
4. Press the axle of the motor against the side<br />
of your jaw.<br />
728 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
KS Studios<br />
Hearing with Your Jaw<br />
Conclude <strong>and</strong> Apply<br />
1. Describe what you heard in your Science<br />
Journal.<br />
2. Identify the form of energy produced by<br />
the radio or CD player.<br />
3. Draw a diagram to show all of the energy<br />
transformations taking place.<br />
4. Evaluate Did anything get hotter as a<br />
result of this activity? Explain.<br />
5. Explain your observations using the law of<br />
conservation of energy.<br />
Compare your conclusions with those of<br />
other students in your class. For more help,<br />
refer to the Science Skill H<strong>and</strong>book.
Sources of <strong>Energy</strong><br />
Using <strong>Energy</strong><br />
Every day, energy is used to provide light <strong>and</strong> to heat <strong>and</strong><br />
cool homes, schools, <strong>and</strong> workplaces. According to the law of<br />
conservation of energy, energy can’t be created or destroyed.<br />
<strong>Energy</strong> only can change form. If a car or refrigerator can’t create<br />
the energy they use, then where does this energy come from?<br />
<strong>Energy</strong> <strong>Resources</strong><br />
<strong>Energy</strong> cannot be made, but must come from the natural<br />
world. As you can see in Figure 16, the surface of Earth<br />
receives energy from two sources—the Sun <strong>and</strong> radioactive<br />
atoms in Earth’s interior. The amount of energy Earth receives<br />
from the Sun is far greater than the amount generated in<br />
Earth’s interior. Nearly all the energy you used today can be<br />
traced to the Sun, even the gasoline used to power the car or<br />
school bus you came to school in.<br />
Radiant energy<br />
from the Sun<br />
Surface of<br />
Earth<br />
Thermal energy from<br />
radioactive atoms<br />
■ Explain what renewable, nonrenewable,<br />
<strong>and</strong> alternative<br />
resources are.<br />
■ Describe the advantages <strong>and</strong><br />
disadvantages of using various<br />
energy sources.<br />
<strong>Energy</strong> is vital for survival <strong>and</strong> making<br />
life comfortable. Developing<br />
new energy sources will improve<br />
modern st<strong>and</strong>ards of living.<br />
Review Vocabulary<br />
resource: a natural feature or<br />
phenomenon that enhances the<br />
quality of life<br />
New Vocabulary<br />
•<br />
nonrenewable resource<br />
•<br />
renewable resource<br />
•<br />
alternative resource<br />
inexhaustible resource<br />
• photovoltaic<br />
Figure 16 All the energy you<br />
use can be traced to one of two<br />
sources—the Sun or radioactive<br />
atoms in Earth’s interior.<br />
SECTION 3 Sources of <strong>Energy</strong> 729
Radiant energy<br />
Figure 17 Coal is formed after<br />
the molecules in ancient plants are<br />
heated under pressure for millions<br />
of years. The energy stored by the<br />
molecules in coal originally came<br />
from the Sun.<br />
<strong>Energy</strong> Source Origins<br />
The kinds of fossil fuels<br />
found in the ground<br />
depend on the kinds of<br />
organisms (animal or plant)<br />
that died <strong>and</strong> were buried<br />
in that spot. Research coal,<br />
oil, <strong>and</strong> natural gas to find<br />
out what types of organisms<br />
were primarily responsible<br />
for producing each.<br />
730 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
Time<br />
Heat<br />
Pressure<br />
Radiant energy from the Sun is<br />
stored as chemical energy in molecules.<br />
Coal mine<br />
Fossil Fuels<br />
Fossil fuels are coal, oil, <strong>and</strong> natural gas. Oil <strong>and</strong> natural gas<br />
were made from the remains of microscopic organisms that<br />
lived in Earth’s oceans millions of years ago. Heat <strong>and</strong> pressure<br />
gradually turned these ancient organisms into oil <strong>and</strong> natural<br />
gas. Coal was formed by a similar process from the remains of<br />
ancient plants that once lived on l<strong>and</strong>, as shown in Figure 17.<br />
Through the process of photosynthesis, ancient plants converted<br />
the radiant energy in sunlight to chemical energy stored<br />
in various types of molecules. Heat <strong>and</strong> pressure changed these<br />
molecules into other types of molecules as fossil fuels formed.<br />
Chemical energy stored in these molecules is released when fossil<br />
fuels are burned.<br />
Using Fossil Fuels The energy used when you ride in a car,<br />
turn on a light, or use an electric appliance usually comes from<br />
burning fossil fuels. However, it takes millions of years to replace<br />
each drop of gasoline <strong>and</strong> each lump of coal that is burned. This<br />
means that the supply of oil on Earth will continue to decrease<br />
as oil is used. An energy source that is used up much faster than<br />
it can be replaced is a nonrenewable resource. Fossil fuels are<br />
nonrenewable resources.<br />
Burning fossil fuels to produce energy also generates chemical<br />
compounds that cause pollution. Each year billions of kilograms<br />
of air pollutants are produced by burning fossil fuels.<br />
These pollutants can cause respiratory illnesses <strong>and</strong> acid rain.<br />
Also, the carbon dioxide gas formed when fossil fuels are burned<br />
might cause Earth’s climate to warm.
Nuclear <strong>Energy</strong><br />
Can you imagine running an automobile on 1 kg of fuel that<br />
releases almost 3 million times more energy than 1 L of gas? What<br />
could supply so much energy from so little mass? The answer is<br />
the nuclei of uranium atoms. Some of these nuclei are unstable<br />
<strong>and</strong> break apart, releasing enormous amounts of energy in the<br />
process. This energy can be used to generate electricity by heating<br />
water to produce steam that spins an electric generator, as shown<br />
in Figure 18. Because no fossil fuels are burned, generating electricity<br />
using nuclear energy helps make the supply of fossil fuels<br />
last longer. Also, unlike fossil fuel power plants, nuclear power<br />
plants produce almost no air pollution. In one year, a typical<br />
nuclear power plant generates enough energy to supply 600,000<br />
homes with power <strong>and</strong> produces only 1 m 3 of waste.<br />
Nuclear Wastes Like all energy sources, nuclear energy has<br />
its advantages <strong>and</strong> disadvantages. One disadvantage is the<br />
amount of uranium in Earth’s crust is nonrenewable. Another is<br />
that the waste produced by nuclear power plants is radioactive<br />
<strong>and</strong> can be dangerous to living things. Some of the materials in<br />
the nuclear waste will remain radioactive for many thous<strong>and</strong>s of<br />
years. As a result the waste must be stored so no radioactivity is<br />
released into the environment for a long time. One method is to<br />
seal the waste in a ceramic material, place the ceramic in protective<br />
containers, <strong>and</strong> then bury the containers far underground.<br />
However, the burial site would have to be chosen carefully so<br />
underground water supplies aren’t contaminated. Also, the site<br />
would have to be safe from earthquakes <strong>and</strong> other natural disasters<br />
that might cause radioactive material to be released.<br />
1. Nuclear energy<br />
of atoms<br />
2. Thermal energy<br />
of water<br />
3. Kinetic energy<br />
of steam<br />
Figure 18 To obtain electrical<br />
energy from nuclear energy, a<br />
series of energy transformations<br />
must occur.<br />
4. Kinetic energy<br />
of turbine<br />
Generator<br />
5. Electrical energy<br />
out of generator<br />
SECTION 3 Sources of <strong>Energy</strong> 731
Topic: Hydroelectricity<br />
Visit green.msscience.com for<br />
Web links to information about the<br />
use of hydroelectricity in various<br />
parts of the world.<br />
Activity On a map of the world,<br />
show where the use of hydroelectricity<br />
is the greatest.<br />
732 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
Hydroelectricity<br />
Currently, transforming the potential energy of water that is<br />
trapped behind dams supplies the world with almost 20 percent<br />
of its electrical energy. Hydroelectricity is the largest renewable<br />
source of energy. A renewable resource is an energy source that<br />
is replenished continually. As long as enough rain <strong>and</strong> snow fall<br />
to keep rivers flowing, hydroelectric power plants can generate<br />
electrical energy, as shown in Figure 19.<br />
Although production of hydroelectricity is largely pollution<br />
free, it has one major problem. It disrupts the life cycle of<br />
aquatic animals, especially fish. This is particularly true in the<br />
Northwest where salmon spawn <strong>and</strong> run. Because salmon<br />
return to the spot where they were hatched to lay their eggs, the<br />
development of dams has hindered a large fraction of salmon<br />
from reproducing. This has greatly reduced the salmon population.<br />
Efforts to correct the problem have resulted in plans to<br />
remove a number of dams. In an attempt to help fish bypass<br />
some dams, fish ladders are being installed. Like most energy<br />
sources, hydroelectricity has advantages <strong>and</strong> disadvantages.<br />
Is energy consumption outpacing production?<br />
You use energy every<br />
day—to get to school,<br />
to watch TV, <strong>and</strong> to heat<br />
or cool your home. The<br />
amount of energy consumed<br />
by an average person<br />
has increased over<br />
time. Consequently,<br />
more energy must be<br />
produced.<br />
<strong>Energy</strong> (quadrillion Btu)<br />
120<br />
Identifying the Problem<br />
The graph above shows the energy produced<br />
<strong>and</strong> consumed in the United States<br />
from 1949 to 1999. How does energy that is<br />
consumed by Americans compare with<br />
energy that is produced in the United States?<br />
Solving the Problem<br />
1. Determine the approximate amount of<br />
energy produced in 1949 <strong>and</strong> in 1999<br />
90<br />
60<br />
30<br />
U.S. <strong>Energy</strong> Overview, 1949–1999<br />
Consumed in<br />
the United States<br />
Produced in<br />
the United States<br />
<strong>Energy</strong> imports<br />
0<br />
1949 1954 1959 1964 1969 1974<br />
Year<br />
1979 1984 1989 1994 1999<br />
<strong>and</strong> how much it has increased in<br />
50 years. Has it doubled or tripled?<br />
2. Do the same for consumption. Has it<br />
doubled or tripled?<br />
3. Using your answers for steps 1 <strong>and</strong> 2 <strong>and</strong><br />
the graph, where does the additional<br />
energy that is needed come from? Give<br />
some examples.
1. Potential energy<br />
of water<br />
2. Kinetic energy<br />
of water<br />
3. Kinetic energy<br />
of turbine<br />
Alternative Sources of <strong>Energy</strong><br />
Electrical energy can be generated in several ways. However,<br />
each has disadvantages that can affect the environment <strong>and</strong> the<br />
quality of life for humans. Research is being done to develop new<br />
sources of energy that are safer <strong>and</strong> cause less harm to the environment.<br />
These sources often are called alternative resources.<br />
These alternative resources include solar energy, wind, <strong>and</strong> geothermal<br />
energy.<br />
Solar <strong>Energy</strong><br />
The Sun is the origin of almost all the energy that is used on<br />
Earth. Because the Sun will go on producing an enormous<br />
amount of energy for billions of years, the Sun is an inexhaustible<br />
source of energy. An inexhaustible resource is an<br />
energy source that can’t be used up by humans.<br />
Each day, on average, the amount of solar energy that strikes<br />
the United States is more than the total amount of energy used<br />
by the entire country in a year. However, less than 0.1 percent of<br />
the energy used in the United States comes directly from the<br />
Sun. One reason is that solar energy is more expensive to use<br />
than fossil fuels. However, as the supply of fossil fuels decreases,<br />
the cost of finding <strong>and</strong> mining these fuels might increase. Then,<br />
it may be cheaper to use solar energy or other energy sources to<br />
generate electricity <strong>and</strong> heat buildings than to use fossil fuels.<br />
What is an inexhaustible energy source?<br />
Figure 19 The potential energy of water behind<br />
a dam supplies the energy to turn the turbine.<br />
Explain why hydroelectric power is a renewable<br />
energy source.<br />
4. Electrical energy<br />
out of generator<br />
Long-distance<br />
power lines<br />
Building a Solar<br />
Collector<br />
Procedure<br />
1. Line a large pot with black<br />
plastic <strong>and</strong> fill with water.<br />
2. Stretch clear-plastic wrap<br />
over the pot <strong>and</strong> tape it<br />
taut.<br />
3. Make a slit in the top <strong>and</strong><br />
slide a thermometer or a<br />
computer probe into the<br />
water.<br />
4. Place your solar collector in<br />
direct sunlight <strong>and</strong> monitor<br />
the temperature change<br />
every 3 min for 15 min.<br />
5. Repeat your experiment<br />
without using any black<br />
plastic.<br />
Analysis<br />
1. Graph the temperature<br />
changes in both setups.<br />
2. Explain how your solar<br />
collector works.<br />
SECTION 3 Sources of <strong>Energy</strong> 733
Figure 20 Solar energy can be<br />
collected <strong>and</strong> utilized by individuals<br />
using thermal collectors or<br />
photovoltaic collectors.<br />
734 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
(t)Dr. Jeremy Burgess/Science Photo Library/Photo Researchers, (b)John Keating/Photo Researchers<br />
Collecting the Sun’s <strong>Energy</strong> Two types of collectors capture<br />
the Sun’s rays. If you look around your neighborhood, you<br />
might see large, rectangular panels attached to the roofs of<br />
buildings or houses. If, as in Figure 20, pipes come out of the<br />
panel, it is a thermal collector. Using a black surface, a thermal<br />
collector heats water by directly absorbing the Sun’s radiant<br />
energy. Water circulating in this system can be heated to<br />
about 70°C. The hot water can be pumped through the house to<br />
provide heat. Also, the hot water can be used for washing <strong>and</strong><br />
bathing. If the panel has no pipes, it is a photovoltaic<br />
(foh toh vol TAY ihk) collector, like the one pictured in<br />
Figure 20. A photovoltaic is a device that transforms radiant<br />
energy directly into electrical energy. Photovoltaics are used to<br />
power calculators <strong>and</strong> satellites, including the International<br />
Space Station.<br />
What does a photovoltaic do?<br />
Geothermal <strong>Energy</strong><br />
Imagine you could take a journey to the center of<br />
Earth—down to about 6,400 km below the surface. As<br />
you went deeper <strong>and</strong> deeper, you would find the temperature<br />
increasing. In fact, after going only about 3 km, the<br />
temperature could have increased enough to boil water.<br />
At a depth of 100 km, the temperature could be over<br />
900°C. The heat generated inside Earth is called geothermal<br />
energy. Some of this heat is produced when unstable<br />
radioactive atoms inside Earth decay, converting nuclear<br />
energy to thermal energy.<br />
At some places deep within Earth the temperature is<br />
hot enough to melt rock. This molten rock, or magma,<br />
can rise up close to the surface through cracks in the<br />
crust. During a volcanic eruption, magma reaches the<br />
surface. In other places, magma gets close to the surface<br />
<strong>and</strong> heats the rock around it.<br />
Geothermal Reservoirs In some regions where<br />
magma is close to the surface, rainwater <strong>and</strong> water from<br />
melted snow can seep down to the hot rock through<br />
cracks <strong>and</strong> other openings in Earth’s surface. The water<br />
then becomes hot <strong>and</strong> sometimes can form steam. The<br />
hot water <strong>and</strong> steam can be trapped under high pressure<br />
in cracks <strong>and</strong> pockets called geothermal reservoirs. In<br />
some places, the hot water <strong>and</strong> steam are close enough to<br />
the surface to form hot springs <strong>and</strong> geysers.
Geothermal Power Plants In places where the geothermal<br />
reservoirs are less than several kilometers deep, wells can be<br />
drilled to reach them. The hot water <strong>and</strong> steam produced by<br />
geothermal energy then can be used by geothermal power<br />
plants, like the one in Figure 21, to generate electricity.<br />
Most geothermal reservoirs contain hot water under high<br />
pressure. Figure 22 shows how these reservoirs can be used to<br />
generate electricity. While geothermal power is an inexhaustible<br />
source of energy, geothermal power plants can be built only in<br />
regions where geothermal reservoirs are close to the surface,<br />
such as in the western United States.<br />
Heat Pumps Geothermal heat helps keep the temperature of<br />
the ground at a depth of several meters at a nearly constant temperature<br />
of about 10° to 20°C. This constant temperature can be<br />
used to cool <strong>and</strong> heat buildings by using a heat pump.<br />
A heat pump contains a water-filled loop of pipe that is<br />
buried to a depth where the temperature is nearly constant. In<br />
summer the air is warmer than this underground temperature.<br />
Warm water from the building is pumped through the pipe<br />
down into the ground. The water cools <strong>and</strong> then is pumped<br />
back to the house where it absorbs more heat, <strong>and</strong> the cycle is<br />
repeated. During the winter, the air is cooler than the ground<br />
below. Then, cool water absorbs heat from the ground <strong>and</strong><br />
releases it into the house.<br />
Hot water from<br />
a geothermal<br />
reservoir forces its<br />
way through a pipe<br />
to the surface where<br />
it turns to steam.<br />
Electric current<br />
Generator<br />
Hot water<br />
Turbine<br />
Cooling towers<br />
The steam turns a<br />
turbine that is<br />
connected to an<br />
electric generator.<br />
Fractures in rock<br />
Cool water<br />
Pump<br />
Figure 21 This geothermal<br />
power plant in Nevada produces<br />
enough electricity to power about<br />
50,000 homes.<br />
Figure 22 The hot water in a<br />
geothermal reservoir is used to<br />
generate electricity in a geothermal<br />
power plant.<br />
The steam is cooled in<br />
the cooling towers <strong>and</strong><br />
condenses into water.<br />
The water is<br />
pumped back<br />
down into the<br />
geothermal<br />
reservoir.<br />
SECTION 3 Sources of <strong>Energy</strong> 735<br />
Geothermal Education Office
Figure 23 This tidal power<br />
plant in Annapolis Royal, Nova<br />
Scotia, is the only operating tidal<br />
power plant in North America.<br />
Figure <strong>24</strong> A tidal power plant<br />
can generate electricity when the<br />
tide is coming in <strong>and</strong> going out.<br />
736 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
<strong>Energy</strong> from the Oceans<br />
The ocean is in constant motion. If you’ve been to<br />
the seashore you’ve seen waves roll in. You may have<br />
seen the level of the ocean rise <strong>and</strong> fall over a period of<br />
about a half day. This rise <strong>and</strong> fall in the ocean level is<br />
called a tide. The constant movement of the ocean is an<br />
inexhaustible source of mechanical energy that can be<br />
converted into electric energy. While methods are still<br />
being developed to convert the motion in ocean waves<br />
to electric energy, several electric power plants using<br />
tidal motion have been built.<br />
Using Tidal <strong>Energy</strong> A high tide <strong>and</strong> a low tide each occur<br />
about twice a day. In most places the level of the ocean changes by<br />
less than a few meters. However, in some places the change is much<br />
greater. In the Bay of Fundy in Eastern Canada, the ocean level<br />
changes by 16 m between high tide <strong>and</strong> low tide. Almost 14 trillion<br />
kg of water move into or out of the bay between high <strong>and</strong> low tide.<br />
Figure 23 shows an electric power plant that has been built<br />
along the Bay of Fundy. This power plant generates enough electric<br />
energy to power about 12,000 homes. The power plant<br />
is constructed so that as the tide rises, water flows through<br />
a turbine that causes an electric generator to spin, as shown in<br />
Figure <strong>24</strong>A. The water is then trapped behind a dam. When the<br />
tide goes out, the trapped water behind the dam is released<br />
through the turbine to generate more electricity, as shown in<br />
Figure <strong>24</strong>B. Each day electric power is generated for about ten<br />
hours when the tide is rising <strong>and</strong> falling.<br />
While tidal energy is a nonpolluting, inexhaustible energy<br />
source, its use is limited. Only in a few places is the difference<br />
between high <strong>and</strong> low tide large enough to enable a large electric<br />
power plant to be built.<br />
Ocean<br />
Turbine Turbine<br />
As the tide comes in, it turns a turbine connected<br />
to a generator. When high tide occurs,<br />
gates are closed that trap water behind a dam.<br />
Cars<strong>and</strong>-Mosher<br />
Ocean<br />
As the tide goes out <strong>and</strong> the ocean level drops,<br />
the gates are opened <strong>and</strong> water from behind the dam<br />
flows through the turbine, causing it to spin <strong>and</strong> turn<br />
a generator.
Wind<br />
Wind is another inexhaustible supply of energy. Modern<br />
windmills, like the ones in Figure 25, convert the kinetic energy<br />
of the wind to electrical energy. The propeller is connected to a<br />
generator so that electrical energy is generated when wind spins<br />
the propeller. These windmills produce almost no pollution.<br />
Some disadvantages are that windmills produce noise <strong>and</strong> that<br />
large areas of l<strong>and</strong> are needed. Also, studies have shown that<br />
birds sometimes are killed by windmills.<br />
Conserving <strong>Energy</strong><br />
Fossil fuels are a valuable resource. Not only are they burned<br />
to provide energy, but oil <strong>and</strong> coal also are used to make plastics<br />
<strong>and</strong> other materials. One way to make the supply of fossil fuels<br />
last longer is to use less energy. Reducing the use of energy is<br />
called conserving energy.<br />
You can conserve energy <strong>and</strong> also save money by turning off<br />
lights <strong>and</strong> appliances such as televisions when you are not using<br />
them. Also keep doors <strong>and</strong> windows closed tightly when it’s cold<br />
or hot to keep heat from leaking out of or into your house.<br />
<strong>Energy</strong> could also be conserved if buildings are properly insulated,<br />
especially around windows. The use of oil could be<br />
reduced if cars were used less <strong>and</strong> made more efficient, so they<br />
went farther on a liter of gas. Recycling materials such as aluminum<br />
cans <strong>and</strong> glass also helps conserve energy.<br />
Summary<br />
Nonrenewable <strong>Resources</strong><br />
• All energy resources have advantages <strong>and</strong> disadvantages.<br />
• Nonrenewable energy resources are used<br />
faster than they are replaced.<br />
• Fossil fuels include oil, coal, <strong>and</strong> natural gas<br />
<strong>and</strong> are nonrenewable resources. Nuclear<br />
energy is a nonrenewable resource.<br />
Renewable <strong>and</strong> Alternative <strong>Resources</strong><br />
• Renewable energy resources, such as hydroelectricity,<br />
are resources that are replenished<br />
continually.<br />
• Alternative energy sources include solar<br />
energy, wind energy, <strong>and</strong> geothermal energy.<br />
green.msscience.com/self_check_quiz<br />
Figure 25 Windmills work<br />
on the same basic principles as a<br />
power plant. Instead of steam turning<br />
a turbine, wind turns the rotors.<br />
Describe some of the advantages<br />
<strong>and</strong> disadvantages of using<br />
windmills.<br />
Self Check<br />
1. Diagram the energy conversions that occur when coal is<br />
formed, <strong>and</strong> then burned to produce thermal energy.<br />
2. Explain why solar energy is considered an inexhaustible<br />
source of energy.<br />
3. Explain how a heat pump is used to both heat <strong>and</strong> cool<br />
a building.<br />
4. Think Critically Identify advantages <strong>and</strong> disadvantages<br />
of using fossil fuels, hydroelectricity, <strong>and</strong> solar energy<br />
as energy sources.<br />
5. Use a Ratio Earth’s temperature increases with depth.<br />
Suppose the temperature increase inside Earth is 500°C<br />
at a depth of 50 km. What is the temperature increase<br />
at a depth of 10 km?<br />
SECTION 3 Sources of <strong>Energy</strong> 737<br />
Billy Hustace/Stone/Getty Images
Goals<br />
■ Identify how energy<br />
you use is produced<br />
<strong>and</strong> delivered.<br />
■ Investigate alternative<br />
sources for the<br />
energy you use.<br />
■ Outline a plan for<br />
how these alternative<br />
sources of energy could<br />
be used.<br />
Data Source<br />
Visit green.msscience.com/<br />
internet_lab for more<br />
information about sources<br />
of energy <strong>and</strong> for data collected<br />
by other students.<br />
738 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
SuperStock<br />
Use the Internet<br />
<strong>Energy</strong> to PKwer<br />
Your Life<br />
Real-World Question<br />
Over the past 100 years, the amount of<br />
energy used in the United States <strong>and</strong> elsewhere<br />
has greatly increased. Today, a number<br />
of energy sources are available, such as<br />
coal, oil, natural gas, nuclear energy, hydroelectric<br />
power, wind, <strong>and</strong> solar energy.<br />
Some of these energy sources are being used<br />
up <strong>and</strong> are nonrenewable, but others are<br />
replaced as fast as they are used <strong>and</strong>, therefore,<br />
are renewable. Some energy sources<br />
are so vast that human usage has almost no<br />
effect on the amount available. These<br />
energy sources are inexhaustible.<br />
Think about the types of energy you use<br />
at home <strong>and</strong> school every day. In this lab,<br />
you will investigate how <strong>and</strong> where energy<br />
is produced, <strong>and</strong> how it gets to you. You will also investigate alternative<br />
ways energy can be produced, <strong>and</strong> whether these sources are<br />
renewable, nonrenewable, or inexhaustible. What are the sources of<br />
the energy you use every day?<br />
Local <strong>Energy</strong> Information<br />
<strong>Energy</strong> Type<br />
Where is that energy produced?<br />
How is that energy produced?<br />
How is that energy delivered to you?<br />
Is the energy source renewable,<br />
nonrenewable, or inexhaustible?<br />
What type of alternative energy<br />
source could you use instead?<br />
Do not write<br />
in this book.
Make a Plan<br />
1. Think about the activities you do every day <strong>and</strong> the things you use. When you<br />
watch television, listen to the radio, ride in a car, use a hair drier, or turn on the<br />
air conditioning, you use energy. Select one activity or appliance that uses energy.<br />
2. Identify the type of energy that is used.<br />
3. Investigate how that energy is produced <strong>and</strong> delivered to you.<br />
4. Determine if the energy source is renewable, nonrenewable, or inexhaustible.<br />
5. If your energy source is nonrenewable, describe how the energy you use could<br />
be produced by renewable sources.<br />
Follow Your Plan<br />
1. Make sure your teacher approves your plan before you start.<br />
2. Organize your findings in a data table, similar to the one that is shown.<br />
Analyze Your Data<br />
1. Describe the process for producing <strong>and</strong> delivering the energy source you<br />
researched. How is it created, <strong>and</strong> how does it get to you?<br />
2. How much energy is produced by the energy source you investigated?<br />
3. Is the energy source you researched renewable, nonrenewable, or inexhaustible?<br />
Why?<br />
Conclude <strong>and</strong> Apply<br />
1. Describe If the energy source you investigated is nonrenewable, how can the use<br />
of this energy source be reduced?<br />
2. Organize What alternative sources of energy<br />
could you use for everyday energy needs? On<br />
the computer, create a plan for using renew-<br />
able or inexhaustible sources.<br />
Find this lab using the link below. Post<br />
your data in the table that is provided.<br />
Compare your data to those of other<br />
students. Combine your data with those<br />
of other students <strong>and</strong> make inferences<br />
using the combined data.<br />
green.msscience.com/internet_lab<br />
LAB 739<br />
Roger Ressmeyer/CORBIS
<strong>Energy</strong> to Burn<br />
Did you know...<br />
... The energy Earth gets each half<br />
hour from the Sun is enough to meet<br />
the world’s dem<strong>and</strong>s for a year. Renewable<br />
<strong>and</strong> inexhaustible resources, including the<br />
Sun, account for only 18 percent of the<br />
energy that is used worldwide.<br />
Write About It<br />
Where would you place solar collectors in the United States? Why? For more<br />
information on solar energy, go to green.msscience.com/science_stats.<br />
740 CHAPTER <strong>24</strong> <strong>Energy</strong> <strong>and</strong> <strong>Energy</strong> <strong>Resources</strong><br />
(tl)Reuters NewMedia, Inc./CORBI, (tr)PhotoDisc, (br)Dominic Oldershaw<br />
... The energy released by the<br />
average hurricane is equal to about<br />
200 times the total energy produced by all<br />
of the world’s power plants. Almost all of<br />
this energy is released as heat when<br />
raindrops form.<br />
... The Calories in one medium<br />
apple will give you enough energy to walk<br />
for about 15 min, swim for about 10 min, or<br />
jog for about 9 min.<br />
If walking for 15 min<br />
requires 80 Calories of fuel (from food), how many Calories<br />
would someone need to consume to walk for 1 h?
What is energy?<br />
1. <strong>Energy</strong> is the ability to cause change.<br />
2. A moving object has kinetic energy that<br />
depends on the object’s mass <strong>and</strong> speed.<br />
3. Potential energy is energy due to position<br />
<strong>and</strong> depends on an object’s mass <strong>and</strong> height.<br />
4. Light carries radiant energy, electric current<br />
carries electrical energy, <strong>and</strong> atomic nuclei<br />
contain nuclear energy.<br />
<strong>Energy</strong> Transformations<br />
1. <strong>Energy</strong> can be transformed from one form<br />
to another. Thermal energy is usually produced<br />
when energy transformations occur.<br />
2. The law of conservation of energy states<br />
that energy cannot be created or destroyed.<br />
3. Electric power plants convert a source<br />
of energy into electrical energy. Steam<br />
spins a turbine which spins an electric<br />
generator.<br />
Sources of <strong>Energy</strong><br />
1. The use of an energy source has advantages<br />
<strong>and</strong> disadvantages.<br />
2. Fossil fuels <strong>and</strong> nuclear energy are nonrenewable<br />
energy sources that are consumed faster<br />
than they can be replaced.<br />
3. Hydroelectricity is a renewable energy<br />
source that is continually being replaced.<br />
4. Alternative energy sources include solar,<br />
wind, <strong>and</strong> geothermal energy. Solar energy<br />
is an inexhaustible energy source.<br />
Copy <strong>and</strong> complete the concept map using the following terms: fossil fuels, hydroelectric, solar,<br />
wind, oil, coal, photovoltaic, <strong>and</strong> nonrenewable resources.<br />
Natural gas<br />
<strong>Energy</strong><br />
<strong>Resources</strong><br />
green.msscience.com/interactive_tutor<br />
Renewable <strong>and</strong><br />
inexhaustible<br />
resources<br />
Thermal<br />
collector<br />
CHAPTER STUDY GUIDE 741<br />
(l)Lowell Georgia/CORBIS, (r)Mark Richards/PhotoEdit, Inc.
alternative resource p. 733<br />
chemical energy p. 719<br />
electrical energy p. 720<br />
energy p. 716<br />
generator p. 726<br />
inexhaustible<br />
resource p. 733<br />
kinetic energy p. 717<br />
law of conservation<br />
of energy p. 722<br />
For each of the terms below, explain the<br />
relationship that exists.<br />
1. electrical energy—nuclear energy<br />
2. turbine—generator<br />
3. photovoltaic—radiant energy—electrical<br />
energy<br />
4. renewable resource—inexhaustible resource<br />
5. potential energy—kinetic energy<br />
6. kinetic energy—electrical energy—<br />
generator<br />
7. thermal energy—radiant energy<br />
8. law of conservation of energy—energy<br />
transformations<br />
9. nonrenewable resource—chemical energy<br />
Choose the word or phrase that best answers the<br />
question.<br />
10. Objects that are able to fall have what type<br />
of energy?<br />
A) kinetic C) potential<br />
B) radiant D) electrical<br />
11. Which form of energy does light have?<br />
A) electrical C) kinetic<br />
B) nuclear D) radiant<br />
742 CHAPTER REVIEW<br />
nonrenewable<br />
resource p. 730<br />
nuclear energy p. 720<br />
photovoltaic p. 734<br />
potential energy p. 718<br />
radiant energy p. 719<br />
renewable resource p. 732<br />
thermal energy p. 718<br />
turbine p. 726<br />
12. Muscles perform what type of energy<br />
transformation?<br />
A) kinetic to potential<br />
B) kinetic to electrical<br />
C) thermal to radiant<br />
D) chemical to kinetic<br />
13. Photovoltaics perform what type of<br />
energy transformation?<br />
A) thermal to radiant<br />
B) kinetic to electrical<br />
C) radiant to electrical<br />
D) electrical to thermal<br />
14. The form of energy that food contains is<br />
which of the following?<br />
A) chemical C) radiant<br />
B) potential D) electrical<br />
15. Solar energy, wind, <strong>and</strong> geothermal are<br />
what type of energy resource?<br />
A) inexhaustible C) nonrenewable<br />
B) inexpensive D) chemical<br />
16. Which of the following is a nonrenewable<br />
source of energy?<br />
A) hydroelectricity<br />
B) nuclear<br />
C) wind<br />
D) solar<br />
17. A generator is NOT required to generate<br />
electrical energy when which of the following<br />
energy sources is used?<br />
A) solar C) hydroelectric<br />
B) wind D) nuclear<br />
18. Which of the following are fossil fuels?<br />
A) gas C) oil<br />
B) coal D) all of these<br />
19. Almost all of the energy that is used on<br />
Earth’s surface comes from which of the<br />
following energy sources?<br />
A) radioactivity C) chemicals<br />
B) the Sun D) wind<br />
green.msscience.com/vocabulary_puzzlemaker
20. Explain how the motion of a swing illustrates<br />
the transformation between potential<br />
<strong>and</strong> kinetic energy.<br />
21. Explain what happens to the kinetic energy<br />
of a skateboard that is coasting along a flat<br />
surface, slows down, <strong>and</strong> comes to a stop.<br />
22. Describe the energy transformations that<br />
occur in the process of toasting a bagel in<br />
an electric toaster.<br />
23. Compare <strong>and</strong> contrast the formation of coal<br />
<strong>and</strong> the formation of oil <strong>and</strong> natural gas.<br />
<strong>24</strong>. Explain the difference between the law of<br />
conservation of energy <strong>and</strong> conserving<br />
energy. How can conserving energy help<br />
prevent energy shortages?<br />
25. Make a Hypothesis about how spacecraft that<br />
travel through the solar system obtain the<br />
energy they need to operate. Do research<br />
to verify your hypothesis.<br />
26. Concept Map Copy <strong>and</strong> complete this concept<br />
map about energy.<br />
Radiant<br />
Forms<br />
<strong>Energy</strong><br />
<strong>Resources</strong><br />
Solar<br />
27. Diagram the energy transformations that<br />
occur when you rub s<strong>and</strong>paper on a piece<br />
of wood <strong>and</strong> the wood becomes warm.<br />
green.msscience.com/chapter_review<br />
28. Multimedia Presentation Alternative sources<br />
of energy that weren’t discussed include<br />
biomass energy, wave energy, <strong>and</strong> hydrogen<br />
fuel cells. Research an alternative<br />
energy source <strong>and</strong> then prepare a digital<br />
slide show about the information you<br />
found. Use the concepts you learned from<br />
this chapter to inform your classmates<br />
about the future prospects of using such<br />
an energy source on a large scale.<br />
29. Calculate Number of Power Plants A certain<br />
type of power plant is designed to provide<br />
energy for 10,000 homes. How many<br />
of these power plants would be needed to<br />
provide energy for 300,000 homes?<br />
Use the table below to answer questions 30 <strong>and</strong> 31.<br />
<strong>Energy</strong> Sources Used<br />
in the United States<br />
<strong>Energy</strong> Source Percent of <strong>Energy</strong> Used<br />
Coal 23%<br />
Oil 39%<br />
Natural gas 23%<br />
Nuclear 8%<br />
Hydroelectric 4%<br />
Other 3%<br />
30. Use Percentages According to the data in<br />
the table above, what percentage of the<br />
energy used in the United States comes<br />
from fossil fuels?<br />
31. Calculate a Ratio How many times greater<br />
is the amount of energy that comes<br />
from fossil fuels than the amount of<br />
energy from all other energy sources?<br />
CHAPTER REVIEW 743
Record your answers on the answer sheet<br />
provided by your teacher or on a sheet of paper.<br />
1. The kinetic energy of a moving object<br />
increases if which of the following occurs?<br />
A. Its mass decreases.<br />
B. Its speed increases.<br />
C. Its height above the ground increases.<br />
D. Its temperature increases.<br />
Use the graph below to answer questions 2–4.<br />
Oil production (billions of barrels)<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
1930<br />
1950<br />
Global Oil Production<br />
1970<br />
1990<br />
Year<br />
2010<br />
2030<br />
2050<br />
2. According to the graph above, in which year<br />
will global oil production be at a maximum?<br />
A. 1974 C. 2010<br />
B. 2002 D. 2050<br />
3. Approximately how many times greater was<br />
oil production in 1970 than oil production<br />
in 1950?<br />
A. 2 times C. 6 times<br />
B. 10 times D. 3 times<br />
4. In which year will the production of oil be<br />
equal to the oil production in 1970?<br />
A. 2010 C. 2022<br />
B. 2015 D. 2028<br />
5. Which of the following energy sources is<br />
being used faster than it can be replaced?<br />
A. tidal C. fossil fuels<br />
B. wind D. hydroelectric<br />
744 STANDARDIZED TEST PRACTICE<br />
Use the circle graph below to answer question 6.<br />
Coal<br />
51%<br />
Nuclear<br />
20%<br />
Gas<br />
14%<br />
Hydro<br />
9%<br />
Oil<br />
3%<br />
Other<br />
renewable<br />
3%<br />
6. The circle graph shows the sources of<br />
electrical energy in the United States. In<br />
2002, the total amount of electrical energy<br />
produced in the United States was 38.2<br />
quads. How much electrical energy was<br />
produced by nuclear power plants?<br />
A. 3.0 quads C. 7.6 quads<br />
B. 3.8 quads D. 35.1 quads<br />
7. When chemical energy is converted into<br />
thermal energy, which of the following<br />
must be true?<br />
A. The total amount of thermal energy plus<br />
chemical energy changes.<br />
B. Only the amount of chemical energy<br />
changes.<br />
C. Only the amount of thermal energy<br />
changes.<br />
D. The total amount of thermal energy plus<br />
chemical energy doesn’t change.<br />
8. A softball player hits a fly ball. Which of the<br />
following describes the energy conversion<br />
that occurs as it falls from its highest point?<br />
A. kinetic to potential<br />
B. potential to kinetic<br />
C. thermal to potential<br />
D. thermal to kinetic
Record your answers on the answer sheet<br />
provided by your teacher or on a sheet of paper.<br />
9. Why is it impossible to build a machine<br />
that produces more energy than it uses?<br />
10. You toss a ball upward <strong>and</strong> then catch it on<br />
the way down. The height of the ball above<br />
the ground when it leaves your h<strong>and</strong> on<br />
the way up <strong>and</strong> when you catch it is the<br />
same. Compare the ball’s kinetic energy<br />
when it leaves your h<strong>and</strong> <strong>and</strong> just before<br />
you catch it.<br />
11. A basket ball is dropped from a height of<br />
2 m <strong>and</strong> another identical basketball is<br />
dropped from a height of 4 m. Which ball<br />
has more kinetic energy just before it hits<br />
the ground?<br />
Use the graph below to answer questions 12 <strong>and</strong> 13.<br />
<strong>Energy</strong> used (quadrillion Btu)<br />
400<br />
350<br />
300<br />
250<br />
200<br />
150<br />
100<br />
50<br />
0<br />
Global <strong>Energy</strong> Use 1970–2000<br />
1970 1975 1980 1985<br />
Year<br />
1990 1995 2000<br />
12. According to the graph above, by about<br />
how many times did the global use of<br />
energy increase from 1970 to 2000?<br />
13. Over which five-year time period was the<br />
increase in global energy use the largest?<br />
Do Your Studying Regularly Do not “cram” the night before<br />
the test. It can hamper your memory <strong>and</strong> make you tired.<br />
green.msscience.com/st<strong>and</strong>ardized_test<br />
Record your answers on a sheet of paper.<br />
14. When you drop a tennis ball, it hits the<br />
floor <strong>and</strong> bounces back up. But it does not<br />
reach the same height as released, <strong>and</strong><br />
each successive upward bounce is smaller<br />
than the one previous. However, you<br />
notice the tennis ball is slightly warmer<br />
after it finishes bouncing. Explain how the<br />
law of conservation of energy is obeyed.<br />
Use the graph below to answer questions 15–17.<br />
Potential energy (J)<br />
15<br />
10<br />
5<br />
0<br />
Potential <strong>Energy</strong> of Batted Ball<br />
5<br />
10<br />
15 20 25<br />
Distance (m)<br />
15. The graph shows how the potential energy<br />
of a batted ball depends on distance from<br />
the batter. At what distances is the kinetic<br />
energy of the ball the greatest?<br />
16. At what distance from the batter is the<br />
height of the ball the greatest?<br />
17. How much less is the kinetic energy of the<br />
ball at a distance of 20 m from the batter<br />
than at a distance of 0 m?<br />
18. List advantages <strong>and</strong> disadvantages of the<br />
following energy sources: fossil fuels,<br />
nuclear energy, <strong>and</strong> geothermal energy.<br />
30<br />
35<br />
40<br />
STANDARDIZED TEST PRACTICE 745